1. Field of the Invention
The present invention relates to a node control device, node device and optical path setting method suitable for establishing an optical network system.
2. Description of Related Art
FIG. 1 shows an aspect of a conventional optical network system. As FIG. 1 shows, the optical network system comprises user terminals 110 connected to routers (or a packet switching machine) 100 and optical cross-connects or optical add-dropmultiplexer (OADM) 130 which are connected with the router 100 and are inter-connected via inter-office optical fibers 120. The optical cross-connect 130 is an device for executing the relay/insertion (add) /extraction (drop) of optical signals and the setting connection of optical signals (that is, optical paths 140) between two node devices which are not necessarily adjacent to each other.
Some of the optical cross-connects 130 do not use wavelength division multiplexing transmission technology, but they also handle optical paths which are optical signal connections given by OCDM or OTDM technology. The many optical cross-connects use a wavelength division multiplexing transmission technology where a plurality of optical signals are sent over one optical fiber, and these multiplexed signals are used as a resource for transmission so as to increase capacity. Actually, the optical cross-connects 130 in FIG. 1 can multiplex a plurality of optical signals having different wavelengths using wavelength multiplexers/demultiplexers and optical spatial switches. An interface 150 is disposed between the router 100 or electronic switching machine (for example, SDH systems or ATM systems) and the optical cross-connect 130 shown in FIG. 1. For this interface 150, wavelength variable (or fix) type O/O (optical/optical) or E/O (Electric/Optical) conversion device and O/E (Optical/Electric) conversion device are used.
Next a packet transmission aspect implemented on such an optical network system will be explained. At first, a packet sent from a user terminal 110 is transmitted to the router 100 via the transmission path. The router 100 analyzes the header of this packet, and transfers the packet to an input interface 150 of the optical path (connection of optical signals) 140 which is set between routers (strictly speaking, an optical path is allocated between interfaces for routers in different nodes) where the destination terminal is connected to or an appropriate router for relaying. By repeating such an operation (packet relay by routers), the transfer target packet reaches the router 100 accommodating the destination user terminal, and is transferred to the destination user terminal 110 via this router.
The optical path 140 shown in FIG. 1 is set by the optical cross-connect (e.g. optical ADM (Add/Drop Multiplexer)) 130 and the optical fiber 120. The input/output interface 150 is disposed between the optical cross-connect 130 and the packet switching machine (e.g. router, electronic switching machine) 100.
Setting of the optical path 140 in the above mentioned optical network system, however, is semi-fixed. So a method for dynamically setting this optical path 140 according to the traffic is under current study.
It is accordingly the first object of the present invention to provide an optical path setting method for dynamically setting an optical path according to the traffic.
It is a second object of the present invention to provide a node control device for such an optical path setting.
It is the third object of the present invention to provide a node device having such a node control device.